Electrostatic toner polymer particles can be prepared by a kind of chemically prepared toner process frequently referred to as “limited coalescence”. In this process, polymer particles having a narrow size distribution are obtained by forming a solution of a polymer in a solvent that is immiscible with water, dispersing the solution so formed in an aqueous medium containing a solid colloidal stabilizer, e.g. colloidal silica, and removing the solvent by evaporation to obtain polymeric particles. The resultant particles are then isolated, treated with base to remove the solid colloid al stabilizer, washed and dried.
The evaporative limited coalescence offers many advantages over the conventional grinding method of producing toner particles. Toner particles can be prepared by the evaporative limited coalescence technique from any type of binder polymer that is soluble in a solvent that is immiscible with water. The size and size distribution of the resulting polymer particles can be controlled by the relative quantities of the polymer employed, the solvent, the quantity and size of the water-insoluble particulate suspension stabilizer and the size to which the solvent-polymer droplets are reduced by the agitation employed in dispersing the organic solution in the aqueous medium. Representative patents disclosing toner manufacture by limited coalescence and advantages thereof include U.S. Pat. Nos. 4,833,060, 4,835,084, 4,965,131, 5,133,992, 6,294,595 6,416,921 and 6,482,562, each of which is incorporated herein by reference.
Following evaporation of the solvent, the isolated particles are typically treated with basic solution to remove the particle stabilizer, e.g. colloid silica. Generally inorganic bases such as sodium or potassium hydroxide are used in this basic treatment process. The use of such strong bases, however, has been found to detrimentally interact with some of the pigments, additives and even polymeric binders useful in toners, and generate less desirable results when using such toners prepared by such process.